As a fifth generation mobile communication system is introduced in the future, it is expected that a radio device such as an access point, for example, a relay apparatus or a base station is located all over a downtown. The relay apparatus according to the background art is used, for example, as a radio backhaul station, which is located in the area beyond the reach of a cable (the area, where it takes too much cost to lay the cable, such as a deep area in mountains and an arterial road) and is connected to a core network through the radio communication with the base station without being connected to a core network through the cable. A service area can be enlarged by a radio multistage relay through the radio backhaul station.
Recently, the radio backhaul station is scheduled to be used in an urban area and the like as well as the area beyond the reach of the cable, in order to lower the cost of laying the cable (for example, see JP-A-2014-216758). Further, since the radio backhaul station does not require a work to lay the cable for the connection with a network, the access point can be additionally provided with degrees of freedom. Accordingly, it is expected that the radio backhaul type, which can performs a relay between the radio devices by radio, spreads in the future.